The present invention is directed generally to the field of disc drives, and more particularly, to an improved assembly for the spindle motor of a disc drive.
Winchester disc drives are used in computers to store increasingly larger amounts of information. A typical Winchester disc drive is a system with a limited number of mechanical parts, including a spindle motor which mounts one or more discs for constant speed rotation, and an actuator carrying a transducer at one end and a voice call motor at the other, and the operable and response to commands to the voice call motor to position the transducer over a selected track on a disc to read and write data.
As one of the most expensive elements in the disc drive, as well as one of the largest and most mechanically complex, many design efforts are intended to minimize the cost and ease of the assembly of the spindle motor. This particular invention is especially directed to improving spindle motor design to incorporate means for grounding the laminations of the stator stack to the shaft while centering the stator stack on the shaft so that it continues to be properly aligned with the magnet supported on the hub which is rotating outside the stator. The need to properly ground the stator stack is long standing and well-established, owing especially to the use of transducers which are increasingly sensitive to any stray electrical fields. Prior efforts to solve this problem, including the separate clip shown in U.S. Pat. No. 5,965,966 incorporated herein by reference, add an additional part to the assembly sequence, and are therefore both expensive and lack the desired level of reliability.
Therefore, it is an object of the present invention to provide an improved spindle motor design of a type especially for use in the disc drive.
A related and more specific objective of the invention is to provide a simplified design for installation of the stator stack over the shaft while effectively grounding the stator stack to the shaft.
Another objective of the invention is to provide means, method and apparatus for fixing the stack on the shaft through radial interference while successfully grounding the stack to the shaft.
Yet another objective of the invention is to minimize the cost of assembling the stack on the shaft, while still electrically grounding the stator stack to the shaft.
These and other objectives of the invention are provided in a spindle motor incorporating a shaft having a known outer diameter and a stator having a known inner diameter which is slightly larger than the outer diameter of the shaft so that it may slip over the shaft. Die cut sharp features are defined in the inner diameter of the stator laminations. These features extending radially inward from the generally circular inner diameter of the stator laminations so that these features establish an interference fit with the outer surface of the shaft which the structure is mounted. When the stack is pressed onto the outer surface of the shaft or base extension to which it is mounted and supported, the coating on the stack will scrape off, thus establishing a metal-to-metal contact between the stack and the adjoining outer surface of the shaft, as a result, a tight interference fit will be established between the inner surface of the stack and the outer surface of the shaft, thus both radially fixing the stack on the shaft, and grounding the stack to the shaft.
Other features and advantages to the present invention will be better understood by reference to the following figures, and the detailed description of the exemplary embodiments given in conjunction with those features.